A device for surveying the radial deformation state of a tire

Abstract

 A device for surveying the radial deformation state of a tire comprises a sensor of the difference between the pressure of the gas inside the tire and the atmospheric pressure; an optical device for outside signalling operating when this difference in pressure decreases under a pre-established threshold value (Fig. 1).

Description

BACKGROUND OF THE INVENTION

[0001] The present invention refers to a device capable of surveying the radial deformation condition of a tire. In particular, said invention relates to an industrialised embodiment resulting suitable for mass production of the device also presenting particular solutions for the employment safety of said device.

PRIOR ART

[0002] EP-A 0 893 284 of applicant discloses a surveying device comprising a sensor capable of identifying the difference between the pressure of the gas inside the tire and the environmental pressure, and of externally signalling when this difference in pressure decreases under a pre-established threshold value. This device is not used for automatic and cheap mass production and it does not present systems assuring the employment safety in any dynamic condition.

AIMS AND FEATURES OF THE INVENTION

[0003] The purpose of the invention is to remedy these defects. The invention, as claimed, solves the problem of creating a device for surveying the radial deformation condition of a tire. By using the present invention the purpose is reached consisting of measuring the radial deformation state of a loaded tire since said deformation is proportional to the difference between the pressure of the gas inside the tire and the environmental pressure.

[0004] A second purpose of the invention is to signal to the external when the difference between the pressure of the gas inside the tire and the environmental pressure decreases under a pre-established threshold value. A further aim is to supply the device with apparatuses assuring the employment safety in every dynamic condition.

[0005] A device according to the present invention comprises an envelope and a threaded body connected each other,
a group freely and axially moving inside the envelope with respect to the threaded body, the group comprising at least a sensor, an amplifier, a transducer and an actuator,
a spring pushing the group towards the end of the envelope distal with respect to the tire,
a gasket integral with the threaded body,
a valve for inflating the tire containing a body fixed by means of a sealing threaded connection, a self-closing member with a sealing gasket sliding inside the threaded connection, hold by a spring in a closing position,
an end of the valve presenting a chamber connected to the internal part of the tire when the self-closing member is open;
the gasket closing the connection between the chamber and the atmosphere when the threaded body is clamped on the valve;
the gasket is clamped by the threaded body by screwing the threaded body until abutting on the external thread of the valve;
a screw mechanism is provided causing the translation of the external envelope with respect to the valve and the threaded body towards the internal part of the tire, the displacement of the group until abutting on the threaded body and the opening of the self-closing member of the valve by means of the action of the end of the housing of the group,
an optical system is provided to signal outside that the group keeps on abutting against the threaded body when the envelope comes back to its distal position.

[0006] The screw mechanism consists of first radial protuberances finding on a cylindrical member,
the cylindrical member is integral with the threaded body,
axial helical contours are located on the first radial protuberances, said axial helical contours resting on homologous axial helical contours, integral with the envelope.

[0007] Second radial protuberances direct to the internal part of the tire are provided in the envelope, the second radial protuberances interfering with peripheral contours integral with the threaded body to prevent the axial translation of the envelope, causing the opening of the self-closing member of the valve in absence of helical movement; said axial translation is due, among other, to the centrifugal force.

[0008] The optical system uses the refraction features of the material of the wall to determine a first colouring, when the group is found far from the wall, and a second colouring, when the group is in contact with the wall.

[0009] The geometrical features of the screw mechanism prevent the relative sliding of the homologous axial helical contours until the clamping couple of the gasket, applied to the external envelope, reaches a pre-established threshold value.

[0010] The threshold value of the clamping couple of the gasket, beyond which the relative sliding of the homologous helical axial contours occurs, depends on the force of a spring pushing the envelope towards the distal position.

[0011] The spring and the geometrical of the screw mechanism realise a right threshold value of the clamping couple of the gasket.

[0012] A hindering mechanism is further provided capable of hindering the displacement of the group until the abutting with the threaded body and the opening of the self-closing member of the valve due to the action of the axial component of the centrifugal force.

[0013] The hindering mechanism comprises a groove located at the end of the threaded body, an elastic ring housed by groove,
the groove is shaped in order to prevent the axial coming out of the ring,
a sleeve is situated between the spring and the group, the sleeve presenting third radial protuberances towards the inside of the tire,
the cylindrical surfaces of the third radial protuberances delimit a zone having an internal diameter shorter than the one of the internal cylinder of the sleeve,
the third radial protuberances have an axial extension limited according to the stroke available for the group in order to allow the disengaging of the protuberances from the elastic ring when the group is found in the distal position with respect to the threaded body,
radial recesses are found in the threaded body,
the radial recesses are capable of housing the third radial protuberances of the sleeve when the group towards the upper wall of the threaded body.

[0014] When the translation of the group towards the upper wall of the threaded body begins, the lower end of each radial protuberance intercepts the ring that, in its rest condition, has an external diameter longer than the one of the cylindrical surfaces,
in order to continue the translation it is necessary an additional axial pushing on the sleeve with respect to the one which exceeds the pushing of the spring, said pushing being capable of overcoming the elastic resistance of the ring and causing the decreasing of the diameter up to allow the passage of the protuberances.

[0015] The obtained additional axial pushing acting on the sleeve exceeds the action of the axial component of the centrifugal force on the group and on the envelope.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other advantages, features and aims of the invention, may be more readily understood by referring to the accompanying drawings, which concern preferred embodiments, in which:

• Fig. 1 shows an axial section of a device according to the present invention in loading condition;
• Fig. 2 represents an axial section of a device according to the present invention in unloading condition;
• Fig. 3 is a perspective view of some internal members of the device;
• Fig. 4 is a sectional view of an internal member of the device;
• Fig. 5 is a perspective of some internal members of the device;
• Fig. 6 is a sectional view of some internal members of the device;
• Fig 7 shows the action of the centrifugal force on the group sensor/amplifier/transducer /actuator and on the external envelope.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

[0017] Fig. 1 shows the device (1) mounted on an usual inflating valve for tires. Said valve substantially consists of a metal tube (2) containing a body (3) the internal of which is fixed by means of a sealed threaded connection (4) in which a self-closing closure member (5) slides. Said member (5), having a sealing gasket (6), is maintained in closing position by a spring (7). The closure member (5) is capable of automatically opening when the pressure, acting on its part facing outside, that is in the chamber (8), multiplied by the effective surface of the sealing gasket (6), generates an axial downwards force higher than the one due to the pressure existing in its inner part, that is in the chamber (9), (inside the tire), multiplied by the efficient surface of the sealing gasket (6) plus the force of the spring (7) or, vice-versa, said closure member (5) is capable of remaining closed when the force due to the pressure in the external part (chamber (8)) is lower than the one due to the pressure existing inside the tire (chamber (9)) plus the force of the spring (7). Of course, the closure member (5) can also be opened from the external part by mechanical action by a force acting on its end and faced towards the internal part as represented in Fig. 1.

[0018] The device (1) is screwed on the valve instead of the usual protection cap. The device (1) and most of its internal components have an axial symmetrical shape. The device (1) comprises a threaded body (11) consisting of two welded parts (11a and 11b); the threaded body (11) engages the threaded end (10) of the inflating valve of the tire. An external envelope (12) is connected to the threaded body (11) through the unscrewing free tripper, surveying the maximum applied torque and generating an axial pushing as below disclosed. The unscrewing function is also used as anti-sabotage and anti-theft.

[0019] Said devices form an unidirectional free tripper, allowing the transmission of a torque between the envelope (12) and the threaded body (11) in the screwing direction only. So doing, when the closure of the whole system is completed and a sufficient clamping torque (capable of contrasting an unscrewing torque) is assured and controlled through apparatuses, as below disclosed, it is impossible to unscrew the system from the valve since the unscrewing torque applied to the envelope (12) cannot be transmitted to the threaded body (11).

[0020] The clamping is necessary to avoid the system can be unscrewed and lost during the movement of the vehicle because of the external forces and vibrations and, moreover, it is necessary to assure the efficiency of the functions to be carried out.

[0021] According to a preferred embodiment as shown in Fig. 3, front teeth (13), that is parallel to the axis of the body, obtained on the external circumference of the threaded body (11), engage homologous axial front teeth (14) obtained on a cylindrical member (15) to be coaxially mounted to the threaded body (11) and capable of a so downwards axially sliding with respect to the threaded body (11) to disengage the homologous teeth, while a spring (16) causes a soft pushing upwards on the cylindrical member (15) tending to maintain the teeth (13, 14) in contact.

[0022] The cylindrical member (15) is fitted with radial protuberances (17) producing on a side axial helical profiles (18) resting on homologous axial helical profiles (19), as shown in Fig. 4, found on the base of the envelope (12) and capable of sliding on them when a proper high screwing torque is applied to the envelope (12), and on the second side axial profiles (20), engaging homologous axial profiles (21) found on the base of the envelope (12) when an unscrewing torque is applied to it.

[0023] So doing, it is possible to transmit a torque in both directions between the envelope (12) and the cylindrical member (15), which can axially translate inside the hollow (22) found on the base of the threaded body (11) and of the envelope (12) against the force of the spring (16).

[0024] Applying a screwing torque on the envelope (12), said torque is also transmitted to the cylindrical member (15), the axial teeth of which (14) engage the homologous axial teeth (13) of the threaded body (11). So doing, the screwing torque is transmitted to the threaded body (11) screwing up to the whole clamping on the end (10) of the valve.

[0025] The clamping of the system on the valve is correctly reached when said clamping is carried out by a not excessive, sufficient and proper final torque. Both in case of manual screwing of the system on the end of the inflating valve of the tire and, above all, in case of using of tools or ancillary equipment for applying a higher clamping torque, the risk is to apply a too much high torque which can damage the system and/or a sealing gasket (23) located between the threaded body (11) and the end (10) of the valve.

[0026] But an excessive clamping torque is not the only problem: also an insufficient clamping torque can result dangerous, since it makes the sealing gasket (23) inefficient and it can just cause the unexpected, even whole, unscrewing of the system because of the vibrations due to the movement of the vehicle.

[0027] For this reason, the system is suitable for assuring, even in case of using by a no skilled person without adequate tools (and, therefore, not able to verify if the applied screwing torque is sufficient for the purpose), the efficient and full clamping of the threaded members (11, 10) and of the gasket (23).

[0028] In the meantime, it can be suggested a solution which assures the full and efficient clamping of the threaded body on the valve, and, therefore, capable of advising the executor of the operation when a screwing torque having a proper and sufficient value for the purpose is obtained, said solution being capable of avoiding an excessive clamping by the application of a screwing torque having a value higher than the proper and sufficient value for the purpose.

[0029] In order to find the above mentioned solution it is suggested, for example, to apply a kind of screwing torque limiting system acting from the external envelope (12) to the threaded body (11) through the free tripper as shown above.

[0030] The torque limiting system is obtained by the coupling of the axial helical profiles (18) and the homologous axial helical profiles (19), capable of sliding on them when a sufficiently high screwing torque is applied to the envelope (12) and capable of generating a component of axial pushing P on the envelope (12) (Fig. 2), the value of which is higher than the upwards pushing due to a spring (24). The spring (24) is located between the threaded body (11) and a centring sleeve (25) by means of which the spring (24) pushes upwards the sensor/amplifier/transducer/actuator group (26) which, before the screwing clamping manoeuvre of the system (1) on the valve, is unloaded and, therefore, rests on the upper wall (27) at the end opposite to the threaded body (11) and rigidly fixed to the envelope (12). The sealing is obtained by means of a gasket (28) located between the end of the envelope (12) and an abutting on the wall (27).

[0031] When the screwing torque applied to the envelope (12) is sufficiently high to generate the component of axial pushing P on the envelope (12) having a value higher than the upwards pushing due to the spring (24), any further increasing of the applied torque causes a helical movement of the envelope (12) which slides towards the valve (2) and, at the same time, causes a pushing from the wall (27) to the sensor/amplifier/transducer/actuator group (26) which, in its turn, presses the spring (24).

[0032] The pushing of the wall (27) on the group (26) causes the translation of the same system towards the upper wall (29) of the threaded body (11) until the abutting. During the descent the lower end (30) of the housing (31) of the group (26) pushes the closure member (5) towards the inside of the valve (2) against the forces of the spring (7) and of the gas pressure of the tire on the efficient section of the gasket (6), and connects the chamber (9) joined to the inside of the tire to the chamber (8) delimited by the end (10) of the valve (2), the upper wall (29) of the threaded body (11), the gasket (23) and by a gasket (32) obtaining the sealing between the lower end (30) of the housing (31) of the group (26) and the cylindrical hollow (33) found on the upper wall (29) of the threaded body (11).

[0033] The gasket (6) is open until the group (26) is displaced towards the threaded body (11), while it automatically closes when the group (26) is far from the threaded body (11).

[0034] The group (26) contains apparatuses suitable for the measuring, amplifying and transducing the signal due to the difference between the gas pressure inside the tire and the environmental pressure and signalling when the pre-established threshold is exceeded.

[0035] These apparatuses are technically equivalent to the ones described in EP-A 0 893 284, therefore, in order to better understand said apparatuses please read this text.

[0036] An annular gasket (35) separates the chamber (36), located between the wall (27) and the group (26), from the chamber (37) located between the centring sleeve (25) and the environment, the chamber (37) communicating with the environment through a not shown hole at the basis of the threaded body (11). This gasket (35) co-operates with the spring (24) in order to realise the same function of the bellows of EP-A 0 893 284.

[0037] The screwing torque applied on the envelope (12) causes the screwing and the system closure (1) on the threaded end (10) of the valve (2) before, and then it causes the helical movement of the envelope (12), the wall (27) of which generates a pushing on the nearest part of the group (26) in order to reach the loading of the device according to EP-A 0 893 284.

[0038] The unscrewing of the system (1) acting on the envelope (12) is prevented by the free tripper if the threaded body (11) is closed during the screwing causing a clamping torque higher than the torque which can be transmitted in screwing direction that is very low but it exists. In order to assure a higher clamping torque, in addition to the usual friction between the two parts, which are fixed by the threading when, both ends are in abutting, further devices can be used, as for example:

Using self-closing technologies of the threaded body (11) on the male thread (10), as for a partial deformation of the female thread of the threaded body (11) or the interposition, at the upper end of the threaded body (11), of a deforming component capable of causing a strong friction torque on the threading (10), as used for self-closing nuts (See Filippi, Disegno di Macchine, Vol. II, Hoepli for some known examples, neither limiting nor exhaustive);

Using further components allowing a strong friction and an high clamping torque between the two parts (11, 10) fixed together, as for example elastic washers like UNI 1751 e 1752 o DIN 128, corrugated or knurled elastic washers, plane or conical elastic washers with toothing according to UNI 3703, 3704, 3705, 3706, etc (See Filippi), which can be applied at the end stop of the male thread (10) in order to avoid any damage to the male thread.

[0039] The elastic washer (34) located between the end (10) of the valve (2) and the upper wall (29) of the threaded body (11) carries out the same function.

[0040] The external contour of the envelope (12) in the clamping zone for the torque (either manually or by using proper tools or manoeuvring keys) has a cylindrical shape or shapes more suitable for a better clamping and a better transmission of the torque, as for example knurling, grooved or polygonal contours.

[0041] The wall (27) is made of transparent material, but its internal contour is shaped by concentric nuts (38) having geometrical features, with respect to the index of refraction of the used material, causing from an external view a neutral colouring when the group (26) is far from the wall (27), Fig. 1, and vice versa a bright colouring according to the tonality of a component (39), shaped with concentric protuberances (40) capable of introducing with precision inside the nuts (38) of the inner part of the wall (27) when the group (26) is found in condition shown in Fig. 2. So doing, the position of the group (26) is signalled to the external part since the neutral colouring corresponds to the system loading, while the bright colouring corresponds to the unloading according to EP-A 0 893 284.

[0042] The sleeve (25) supports the group (26), to which transmits the pushing of the spring (24). An apparatus is provided suitable to prevent the translation of the group (26) from the unloading condition of Fig. 2 in which it is fixed to the wall (27) towards the upper wall (29) of the threaded body (11) because of the centrifugal force due to the rotation of the wheel, said force acting on the group (26) and on the envelope (12).

[0043] The apparatus is better shown in Figs 5, 6. The sleeve (25) of Fig 5 presents radial protuberances (42) towards the inside, the cylindrical surfaces (46) of which delimit a zone having an internal diameter shorter than the one of the internal cylinder of the sleeve (25). The protuberances (42) have an axial extension limited according to the stroke available for the group (26) inside the chamber (36), in order to allow the disengaging of the protuberances from an open elastic ring (41) when the group (26) is in contact with the wall (27). The elastic ring (41) is found inside a groove (43) being in the upper part of the threaded body (11b) shaped in order to prevent the axial coming out of the ring (41). Radial recesses (44) are found in the threaded body (11b), said recesses capable of housing the radial protuberances (42) of the sleeve (25) when the group (26) translates towards the upper wall (29) of the threaded body (11).

[0044] When the translation of the group (26) towards the upper wall (29) of the threaded body (11) begins, the lower end (45) of each radial protuberance (42) intercepts the ring (41) which, in its rest condition, has an external diameter longer than the one of the cylindrical surfaces (46). In order to continue the translation, it is necessary an additional axial pushing on the sleeve (25) with respect to the one which exceeds the pushing of the spring (24), said pushing being capable of overcoming the elastic resistance of the ring (41) and causing the decreasing of the diameter up to allow the passage of the protuberances (42).

[0045] If the action of the centrifugal force on the group (26) and on the envelope (12) is lower than the additional pushing the translation of the group (26) is stopped. The elastic reaction of the ring (41) and the shaping of the radial protuberances (42), and in particular of their lower ends (45), are so planed to cause the stopping of the translation of the group (26) and the envelope (12) due to the action of the centrifugal forces also very high with respect to the speed of the vehicle.

[0046] A stopping of the descent of the envelope (12) in case of translation without helical movement, as in case of action due to the centrifugal force only, is then realised by means of further radial protuberances found on the external contour of the cylindrical member (15) extending the basis of the protuberances (17), as shown in Fig 3, by peripheral contours (46). In the envelope (12) radial protuberances (47) towards inside are found (Fig 4), which interfere with the peripheral contours (46) in case of translation of the envelope (12) without helical movement, for example because of the centrifugal force, as shown in Fig 7.

[0047] The centrifugal force, due to the rotation of the wheel, presents a component a_ca pushing the device together with all its parts towards the internal part of the wheel. The push tends to cause the translation of the parts moving with respect to the envelope (12), including the group (26) and the closure member (5).

Claims

1. A device for surveying the radial deformation condition of a tire, characterised by an envelope (12) and a threaded body (11, 11a, 11b) connected each other,
a group (26) freely and axially moving inside the (12) with respect to the threaded body (11, 11a, 11b),
the group (26) comprising at least a sensor, an amplifier, a transducer and an actuator, a spring (24) pushing the group (26) towards the end of the envelope (12) distal with respect to the tire, a gasket (23) integral with the threaded body (11, 11a, 11b),
a valve (2) for inflating the tire containing a body (3) fixed by means of a sealing threaded connection (4), a self-closing member (5) with a sealing gasket (6), slides inside the threaded connection (4), hold by a spring (7) in a closing position,
an end of the valve (2) presents a chamber (8) connected to the internal part of the tire when the self-closing member (5) is open;
the gasket (23) closes the connection between the chamber (8) and the atmosphere when the threaded body (11, 11a, 11b) is clamped on the valve (2);
the gasket (23) is clamped by the threaded body (11, 11a, 11b) by screwing the threaded body (11, 11a, 11b) until abutting on the external thread (10) of the valve (2);
a screw mechanism is provided causing the translation of the external envelope (12) with respect to the valve (2) and the threaded body (11, 11a, 11b) towards the internal part of the tire, the displacement of the group (26) until abutting on the threaded body (11, 11a, 11b) and the opening of the self-closing member (5) of the valve (2) by means of the action of the end (30) of the housing (31) of the group (26),
an optical system is provided to signal outside that the group (26) keeps on abutting against the threaded body (11, 11a, 11b) when the envelope (12) comes back to its distal position.

2. A device as in claim 1, wherein the screw mechanism consists of first radial protuberances (17) finding on a cylindrical member (15),
the cylindrical member (15) is integral with the threaded body (11, 11a, 11b),
axial helical contours (18) are located on the first radial protuberances (17), said axial helical contours (18) resting on homologous axial helical contours (19), integral with the envelope (12).

3. A device as in claim 1, wherein second radial protuberances (47) direct to the internal part of the tire are provided in the envelope (12), the second radial protuberances (47) interfering with peripheral contours (46) integral with the threaded body (11, 11a, 11b) to prevent the axial translation of the envelope (12), causing the opening of the self-closing member (5) of the valve (2) in absence of helical movement; said axial translation is due to an external force (centrifugal force).

4. A device as in claim 1, wherein the optical system uses the refraction features of the material of the wall (27) to determine a first colouring, when the group (26) is found far from the wall (27), and a second colouring, when the group (26) is in contact with the wall (27).

5. A device as in claim 1, wherein the geometrical features of the screw mechanism prevent the relative sliding of the homologous axial helical contours (18, 19) until the clamping couple of the gasket (23), applied to the external envelope, (12) reaches a pre-established threshold value.

6. A device as in claim 1, wherein the threshold value of the clamping couple of the gasket (23), beyond which the relative sliding of the homologous helical axial contours occurs (18, 19), depends on the force of a spring (24) pushing the envelope (12) towards the distal position.

7. A device as in claim 1, wherein the spring (24) and the geometrical of the screw mechanism realise a right threshold value of the clamping couple of the gasket (23).

8. A device as in claim 1, wherein a hindering mechanism is further provided capable of hindering the displacement of the group (26) until the abutting with the threaded body (11, 11a, 11b) and the opening of the self-closing member (5) of the valve (2) due to the action of the axial component of the centrifugal force.

9. A device as in claim 1, wherein the hindering mechanism comprises a groove (43) located at the end of the threaded body (11, 11a, 11b), an elastic ring (41) housed by groove (43 ),
the groove (43) is shaped in order to prevent the axial coming out of the ring (41),
a sleeve (25) is situated between the spring (24) and the group (26), the sleeve (25) presenting third radial protuberances (42) towards the inside of the tire,
the cylindrical surfaces (46) of the third radial protuberances (42) delimit a zone having an internal diameter shorter than the one of the internal cylinder of the sleeve (25),
the third radial protuberances (42) have an axial extension limited according to the stroke available for the group (26) in order to allow the disengaging of the protuberances (42) from the elastic ring (41) when the group (26) is found in the distal position with respect to the threaded body (11, 11a, 11b),
radial recesses (44) are found in the threaded body (11, 11a, 11b),
the radial recesses (44) are capable of housing the third radial protuberances (42) of the sleeve (25) when the group (26) slides towards the upper wall (29) of the threaded body (11, 11a, 11b).

10. A device as in claim 1, wherein, when the translation of the group (26) towards the upper wall (29) of the threaded body (11, 11a, 11b) begins, the lower end (45) of each radial protuberance (42) intercepts the ring (41) that, in its rest condition, has an external diameter longer than the one of the cylindrical surfaces (46),
in order to continue the translation it is necessary an additional axial pushing on the sleeve (25) with respect to the one which exceeds the pushing of the spring (24), said pushing being capable of overcoming the elastic resistance of the ring (41) and causing the decreasing of the diameter up to allow the passage of the protuberances (42),
the obtained additional axial pushing acting on the sleeve (25) exceeds the action of the axial component of the centrifugal force on the group (26) and on the envelope (12).

Drawing